Three carbon alkane gas aka Propane is stored under pressure inside a tank. It is a colorless and odorless liquid. The Interesting thing is when propane is brought into the liquid form it will weigh half the weight of the same amount of water.

So, How Much Does A Gallon Of Propane Weigh?
One Gallon of U.S. propane weighs 4.23 pounds or 1.91 kg.
How Much Does A Gallon Of Propane Cost?
The price of propane varies throughout the year. It depends on supply and demand. Your location and season are other factors that can determine propane price.
Currently the average price of a gallon of propane is $2 to $2.75. However depending on companies refill offerings it may be as much as
$3.25 to $4.00 per gallon.
Fun Facts:
>>Propane is an odorless gas and odourant is added to its tank to detect leaks.
>>To burn one cubic foot of propane you will need about 24 cubic feet of air.
>>Propane is one of the lightest hydrocarbons in existence.
>>Propane is not greenhouse gas.